This invention relates to riveting devices and more particularly to devices for effecting what is known in the art as slug riveting.
In slug riveting the blank rivets are plain cylindrical members which are inserted in workpieces and both ends of the slug are upset after such insertion to form rivet heads at opposite sides of the workpieces. In prior art apparatus of this general class a substantial problem has existed in effectively feeding rivet blanks or slugs to the riveting mechanism and in inserting the blanks in the rivet holes of the workpieces.
The achievement of these objects in prior art slug riveting apparatus is further complicated by the necessity for accurately controlling the axial position of the rivet blank or slug so that the slug projects the proper distance from the work at opposite sides thereof at all stages of the inserting and head forming operations. This latter necessity must be met so that the proper amount of blank material is present at opposite sides of the work to properly form heads at the opposite sides of the work.
A further problem in prior art slug riveting has been the difficulty of maintaining the rivet slug in an accurately aligned position coaxial with the rivet head forming anvils.
In prior art slug riveting it has been necessary to rely upon the holes in the work pieces for locating the rivet slugs in a radial direction but the necessary clearance or tolerance between the slug diameter and the hole diameter is such that accurate axial alignment of the rivet slug cannot be achieved. In fact, the problem of rivet slug alignment is of such an aggravated nature that with relatively thin work pieces reliance on the holes in the work pieces for locating the rivet slugs is ineffectual and it is accepted in the present state of the art that whenever the thickness of the work pieces is less than about 60 percent of the rivet diameter slug riveting cannot be employed.
This problem is even greater in the case of riveting work wherein steel rivets are to be applied to punched holes in work pieces since in this case even greater tolerances are required as between the rivet slug diameter and the diameter of the punched holes in the work pieces.